The present disclosure relates to systems, devices, and methods for percutaneous implantation of a prosthetic heart valve. More particularly, it relates to systems, devices, and methods for percutaneously remodeling an implanted stented prosthetic heart valve.
Diseased or otherwise deficient heart valves can be repaired or replaced with an implanted prosthetic heart valve. Conventionally, heart valve replacement surgery is an open-heart procedure conducted under general anesthesia, during which the heart is stopped and blood flow is controlled by a heart-lung bypass machine. Traditional open surgery inflicts significant patient trauma and discomfort, and exposes the patient to a number of potential risks, such as infection, stroke, renal failure, and adverse effects associated with the use of the heart-lung bypass machine, for example.
Due to the drawbacks of open-heart surgical procedures, there has been an increased interest in minimally invasive and percutaneous replacement of cardiac valves. With percutaneous transcatheter (or transluminal) techniques, a valve prosthesis is compacted for delivery in a catheter and then advanced, for example, through an opening in the femoral artery and through the descending aorta to the heart, where the prosthesis is then deployed in the annulus of the valve to be replaced (e.g., the aortic valve annulus). Although transcatheter techniques have attained widespread acceptance with respect to the delivery of conventional stents to restore vessel patency, only mixed results have been realized with percutaneous delivery of the more complex prosthetic heart valve.
Various types and configurations of prosthetic heart valves are available for percutaneous valve procedures, and continue to be refined. The actual shape and configuration of any particular transcatheter prosthetic heart valve is dependent to some extent upon the native shape and size of the valve being repaired (i.e., mitral valve, tricuspid valve, aortic valve, or pulmonary valve). In general, prosthetic heart valve designs attempt to replicate the functions of the valve being replaced and thus will include valve leaflet-like structures. With a bioprostheses construction, the replacement valve may include a valved vein segment that is mounted in some manner within an expandable stent frame to make a valved stent (or “stented prosthetic heart valve”). For many percutaneous delivery and implantation devices, the stent frame of the valved stent is made of a self-expanding material and construction. With these devices, the valved stent is crimped down to a desired size and held in that compressed arrangement within an outer sheath, for example. Retracting the sheath from the valved stent allows the stent to self-expand to a larger diameter, such as when the valved stent is in a desired position within a patient. In other percutaneous implantation systems, the valved stent can be initially provided in an expanded or uncrimped condition, then crimped or compressed on a balloon portion of a catheter until it is as close to the diameter of the catheter as possible. Once delivered to the implantation site, the balloon is inflated to deploy the prosthesis. With either of these types of percutaneous stented valve delivery devices, conventional sewing of the prosthetic heart valve to the patient's native tissue is typically not necessary.
With transcatheter delivery, it is imperative that the stented prosthetic heart valve be accurately located relative to the native annulus immediately prior to full deployment from the catheter as successful implantation requires the prosthetic heart valve to intimately lodge and seal against the native annulus. If the prosthesis is incorrectly positioned relative to the native annulus, serious complications can result such as leaks or even dislodgement from the native valve implantation site. Further, even if optimally located, problems may arise if the implanted prosthesis does not closely “fit” the native anatomy, including paravalvular leakage, migration due to hydrodynamic forces, and damage to surrounding tissues (e.g., aorta, cardiac tissue, etc.). As a point of reference, these same concerns do not normally arise in the context of conventional vascular stent implantation; with these procedures, the stent will perform its intended function regardless of whether the expanded shape closely matches the native anatomy.
In light of the above concerns, a clinician may employ imaging technology to evaluate the native heart valve anatomy prior to performing the implantation procedure, selecting an optimally sized prosthesis based on the evaluation. However, only the size of the selected prosthesis is affected by this evaluation, and not the overall shape. Thus, while the differently sized transcatheter prosthetic heart valves made available to the clinician are generally shaped in accordance with the expected native valve anatomy, it is unlikely that a selected prosthesis will actually “match” the actual native shape. Further, there are significant limitations associated with current imaging-based sizing procedures for transcatheter prosthetic heart valves. For example, measurements are currently only taken in one or two dimensional views and therefore may not account for annular ellipticity; identifying the true leaflet basal hinge point can be difficult with calcification, imaging errors, and the non-orthogonal geometry of a tricuspid valve; unknown annular compliance makes cross-sectional geometry of an implanted stent frame difficult to predict, which can lead to unacceptable stent aspect ratios and replacement valve performance; and variable calcification profiles may interact unpredictably with the stent frame. Unfortunately, conventional transcatheter prosthetic heart valve implantation devices do not readily permit in situ remodeling or shaping of a deployed heart valve prosthesis.
In light of the above, a need exists for transcatheter prosthetic heart valve delivery systems and methods that facilitate modeling of an implanted prosthesis to the native valve anatomy.